Waveguide couplers

ABSTRACT

A method of making a waveguide coupler consists of forming each of the two portions of the coupler by a metal coating or deposition process. In such a coupler coupling apertures are formed between the two portions partly during the coating or deposition process. The method is versatile and avoids undesirable effects previously exhibited by a coupler formed by simply joining a part of pre-fabricated portions of coupler together.

United States Patent Wade 1 1 Oct. 1, 1974 {54] WAVEGUIDE COUPLERS 3,105,285 10/1963 Favre 29/600 3,245,132 4/1966 Thal r 1 29/600 [75] Inventor Regmald Peter Wade Dunmow, 3,299,492 1/1967 SargZnt 29 600 England 3,413,640 11/1968 Freeman et al..,.. 156/18 [73] Assigneez The Marconi Company Limited, 3,613,230 10/1971 Griff 29/600 Essex, England Primary ExaminerC. W. Lanham [22] Flled' 1972 Assistant Examiner-James R. Duzan 1 1 PP 304,991 Attorney, Agent, or FirmBaldwin, Wight & Brown [30] Foreign Application Priority Data 57] ABSTRACT Nov. 9, .1971 Great Brltam 51906/71 A method of making a waveguide coupler consists of [52] US. Cl 29/600, 117/130 R, 156/2, forming each of the two portions of the coupler by a 156/3 metal coating or deposition process. In such a coupler [51] Int. Cl. H0lp 11/00 coupling apertures are formed between the two por- [58] Field of Search 29/600; 333/95, 96, 97, tions partly during the coating or deposition process. 333/98; 117/130 R, 131, 230, 217; 156/2, 3, The method is versatile and avoids undesirable effects 18 previously exhibited by a coupler formed by simply joining a part of pre-fabricated portions of coupler to- [56] References Cited gether.

UNITED STATES PATENTS 15 Cl 8 D F 2,898,273 8/1959 Forge et a1 29 600 alms gums r: .I1-' T.l ::::z ...'1- L .C\

WAVEGUIDE COUPLERS This invention relates to waveguide couplers and more particularly to methods of making waveguide couplers.

A known method of making a waveguide coupler which is capable of coupling between two lengths of waveguide comprises taking two conductive waveguide members one shaped and dimensioned in accordance with the parameters of one of the lengths of waveguide to be coupled and the other with the other and each with a wall omitted through which coupling is to be per formed, and sandwiching a sheet of conductive material with coupling apertures formed therein between the open faces of the two conductive waveguide members. The joints between both the conductive waveguide members and the sheet of conductive material are then soft soldered, thus producing a seam fillet along two edges of both waveguide members. The fillet however is most undesirable for many modes of wave propagation and leads to a disturbance of the electric E field in the coupler.

The present invention seeks to provide methods of making a waveguide coupler in which the aforementioned electric field disturbances are substantially reduced and improved waveguide couplers made by such methods.

According to this invention in its broadest aspect a method of making a waveguide coupler includes the steps of coating the outer surface of a mandrel having the cross-sectional dimensions and shape of a required first length of waveguide with a thin walled conductive waveguide member; etching a plurality of apertures through a portion of said conductive member; closing said apertures with a soluble material; and providing a further conductive material coating to form a second length of waveguide over said apertures.

According to one aspect of this invention a method of making a waveguide coupler includes the steps of coating the outer surface of a mandrel having the crosssectional dimensions and shape of a required first length of waveguide with a thin walled conductive waveguide member; etching a plurality of coupling apertures through a portion of said conductive member; closing said apertures with a soluble material; further coating with another conductive member, removing part of said other conductive member to expose said apertures in saidfirst member and to form a cavity which constitutes part of the interior of said second required length of waveguide; dissolving said soluble material; forming a section constituting the remaining part cross-section of said second length and fixing this to said other conductive member to form said second required length of waveguide.

Preferably said cavity constituting part of the interior wall of said second length of waveguide has a depth substantially one half the inside broad wall dimension of said second length of waveguide and said cavity is formed to be of width substantially equal to the narrow wall dimension of said second length of waveguide.

The mandrel may be removed at any convenient time e.g., before dissolving the soluble material or after steps the remaining part section to said other conductive member. member;

According to a further aspect of this invention a method of making a waveguide coupler includes the step of coating the outer surface of a mandrel having the cross-sectional dimensions and shape of a required first length of waveguide with a thin walled conductive waveguide member; etching a plurality of apertures through a portion of said conductive memberl closing said apertures with a soluble material; providing a further mandrel having the cross-sectional dimensions and shape corresponding with the internal cross-sectional dimensions and shape of a required second length of waveguide to cover said apertures; coating the outer surface of the thin walled conductive waveguide member and the further mandrel with another conductive waveguide member; removing said mandrel and said further mandrel; and dissolving said soluble material.

Preferably the thin walled conductive waveguide member and the other conductive waveguide member are the same material.

Preferably the mandrel and the further mandrel are manufactured from brass and prepared for use by oxidising sufficiently to prevent adhesion of the conductive waveguide members thereto.

Preferably the thin walled inner conductive waveguide member is substantially .006" thick copper.

Preferably the soluble material is that known under the Registered Trade Mark Araldite" and the solvent used is methylene chloride.

The invention of a method for making a waveguide coupler will now be described by way of example with reference to the accompanying drawings, in which FIG. 1 is an elevational view of a mandrel used in the method of this invention;

FIG. 2 is an end view of the mandrel of FIG. 1;

FIG. 3 is an elevational view of the mandrel during one stage of coupler manufacture;

FIG. 4 is an end view of the structure in FIG. 3 indicating the next stage of manufacture;

FIG. 5 is a plan view illustrating the finished product;

FIG. 6 is a cross section taken along section line 6-6 of FIG. 5;

FIG. 7 is a view similar to FIG. 3 but showing a modification; and

FIG. 8 is an end view of the assembly shown in FIG. 7.

In the figures like numbers denote like parts.

Referring to FIGS. 1 and 2 a circular brass mandrel l is machined over part of its length to form a semicircle 2 of predetermined dimensions, the semi-circular shape being formed to that required for the internal cross-section of a first length of waveguide. An oxide layer (not shown) is grown on the mandrel l to prevent copper, deposited at a later stage of manufacture, from adhering thereto. However, the oxide layer is required to be sufficiently thin to permit copper to be attracted to the brass mandrel 1 during the stages of electrodeposition to be described later. A preferred thickness for the oxide layer is three microns. Dowel holes 3, one eighth of an inch in diameter are machined at opposite ends on the centre line of the flat face of the semicircle 2. The area surrounding the dowel holes 3 is then masked as shown by the shaded areas 4 to prevent copper, which is deposited in the next stage of manufacture from entering the dowel holes 3. A layer of copper 5 is now electro-deposited on the semicircular part 2 of the brass mandrel l to a depth of 0.008 inch. The surface of the deposited copper 5 is then smoothed to remove nodules formed as a result of the deposition process.

Referring to FIGS. 3 and 4 the flat face of the semicircle 2 is coated with photo-resist (not shown) and a photolithographic mask (also not shown) containing the shapes and positions of coupling apertures 6 is placed over the dowel holes 3 and located by dowels (not shown) in the dowel holes 3. Using known photolithographic and etching techniques the copper 5 where the apertures 6 are situated is completely etched away. The apertures 6 are filled with epoxy resin known under the Registered Trade Mark Araldite.

Electro-deposition of copper is now continued to form a block 7 which has a thickness of half the broad wall width of a rectangular second length of waveguide 8. Typically the thickness of the block 7 is 0.125 inch.

The outer surface of the block 7 is now machined to fit inside flanges 9 and the block 7 and the flanges 9 are then soft soldered together. A channel 10 the width of the narrow wall of guide length 8 is cut through the block 7 to within 0.005 inch of the mandrel 1, thereby revealing the coupling apertures 6. The mandrel 1 is now removed and the epoxy resin inside the apertures 6 dissolved using methylene chloride as a solvent.

A block of copper 11 is now machined to form a slot 12 having a width the same as the narrow wall width of guide length 8 and a depth the same as half the width of the broad wall of guide length 8. Flanges 13 are soft soldered to the block 11 and the blocks 7 and 11 are bolted together by bolts not shown.

It may be noted that if a coupler of the centre excited type is required, instead of providing the block 11 a mirror image of the block 7 may be manufactured and the block 7 and its mirror image may then be bolted together.

The foregoing description was for a coupler in which coupling may be performed between a semi-circular length of waveguide and a narrow wall of a rectangular length of waveguide. So that the coupling apertures 6 cut the electric E field in the rectangular length of waveguide, to be operated in the TE mode, they are spaced, as shown in FIG. 3, on the centre line of the coupler. A further aspect of the present invention will now be described whereby coupling is to be performed between a semicircular length of waveguide and a broad wall of a rectangular length of waveguide operated in the TE mode. Because coupling is performed to the broad wall of the rectangular length of waveguide it will be seen with reference to FIG. 4 that the coupling apertures 6 are now situated on both sides of the centre line of the coupler to be manufactured.

Referring to FIG. 7 the brass mandrel l is shaped, oxidised, provided with dowel holes 3, masked electrodeposited with copper, photolithographically etched and the apertures 6 filled with an epoxy resin as has al ready been described with reference to the foregoing figures. However, instead of depositing block 7 directly over the apertures 6 a further brass mandrel 14 of the required internal cross section for the second length of waveguide, which is rectangular in the illustrated embodiment, is covered with an oxide layer similar to that layer covering mandrel l, and placed with the centre line of a broad wall thereof over the coupling apertures 6. Copper block 7 is now electro-deposited to a depth of 0.050 inch over the further mandrel l4 and the previously deposited copper 5. The external surfaces of the deposited copper are now machined as required to provide a rectangular shape. The mandrels l and 14 are now removed and the epoxy resin dissolved using methylene chloride. Waveguide flanges (not shown) of known form per se are now soft soldered at opposite, open ends of the deposited block 7.

Although the methods above described related only to the manufacture of semicircular to rectangular waveguide couplers the invention is not intended to be so limited since many forms of coupler having varying sections may also be manufactured using the methods in accordance with this invention. For example, a coupler having sections. circular to square, or elliptical to sectorial or rectangular to triangular may also be manufactured using one or other of the above methods. Also, the dimensions given in this specification are by way of practical example only and the invention is not limited by their adoption.

lclaim:

1. A method of making a waveguide coupler including the steps of coating the outer surface of a mandrel having the cross-sectional dimensions and shape of a required first length of waveguide with a thin walled conductive waveguide member; etching a plurality of apertures through a portion of said conductive member; closing said apertures with a soluble material; providing a further conductive materialcoating to form a second length of waveguide over said apertures; and removing said mandrel and dissolving said soluble material.

2. A method of making a waveguide coupler including the steps of coating the outer surface of a mandrel having the cross-sectional dimensions and shape of a required first length of waveguide with a thin walled conductive waveguide member; etching a plurality of coupling apertures through a portion of said conductive member; closing said apertures with a soluble material; further coating with another conductive member, removing part of said other conductive member to expose said apertures in said first member and to form a cavity which constitutes part of the interior of said second required length of waveguide; removing said mandrel and dissolving said soluble material; forming a section constituting the remaining part cross-section of said second length and fixing this to said other conductive member to form said second required length of waveguide.

3. A method of making a waveguide coupler according to claim 2 wherein said cavity constituting part of the interior wall of said second length of waveguide has a depth substantially one half the inside broad wall dimension of said second length of waveguide and said cavity is formed to be of width substantially equal to the narrow wall dimension of said second length of waveguide.

4. A method of making a waveguide coupler including the steps of coating the outer surface of a mandrel having the cross-sectional dimensions and shape of a required first length of waveguide with a thin walled conductive waveguide member; etching a plurality of apertures through a portion of said conductive member; closing said apertures with a soluble material; providing a further mandrel having the cross-sectional dimensions and shape corresponding with the internal cross-sectional dimensions and shape of a required second length of waveguide to cover said apertures; coating the outer surface of the thin walled conductive waveguide member and the further mandrel with another conductive waveguide member; removing said mandrel and said further mandrel; and dissolving said soluble material.

5. A method of making a waveguide coupler as claimed in claim 2 wherein the thin walled conductive waveguide member and the other conductive waveguide member are the same material.

6. A method of making a waveguide coupler as claimed in claim 4 wherein the mandrel and the further mandrel are manufactured from brass and prepared for use by oxidising sufficiently to prevent adhesion of the conductive waveguide members thereto.

7. A method of making a waveguide coupler as claimed in claim 1 wherein the thin walled inner conductive waveguide member is substantially 0.006 inch thick copper.

8. A method of making a waveguide coupler as claimed in claim 2 wherein the soluble material is an epoxy resin and the solvent used is methylene chloride.

9. A method of making a waveguide coupler as claimed in claim 4 wherein the thin walled conductive waveguide member and the other conductive waveguide member are the same material.

10. A method of making a waveguide coupler as claimed in claim 4 wherein the soluble'material is that known under the Registered Trade Mark Araldite and the solvent used is methylene chloride.

11. The method of making a waveguide coupler, comprising the steps of:

a. coating the outer surface of a mandrel with a first,

thin layer of conductive material to define interiorly thereof a first waveguide section;

b. etching through said first layer to provide a plurality of apertures therein communicating with said first waveguide section;

c. blocking off said apertures;

d. forming a second waveguide section extending along over said apertures;

e. removing said mandrel; and then f. unblocking said apertures to interconnect said first and second waveguide sections through said apertures;

the forming of step (d) including coating additional conductive material onto said first, thin layer.

12. The method of making a waveguide coupler,

comprising the steps of:

a. coating the outer surface of a mandrel with a first, thin layer of metallic material to define a body of selected length presenting a first waveguide section interiorly thereof;

b. etching through said first layer to provide a plurality of apertures therein communicating with said first waveguide section and spaced longitudinally with respect thereto;

c. filling said apertures with soluble material;

d. coating the outer surface of said body with a second metallic layer which is substantially thicker than said first layer and is integrally joined thereto;

e. cutting a channel through said second layer from one end of said body to the opposite end thereof and located to expose said soluble material at the bottom of said channel;

f. removing said mandrel from within said body and dissolving away said soluble material;

g. forming a block to the length of said body and to engage in face-to-face contact therewith to close the top of said channel and define with the channel a portion of a second waveguide section;

h. forming opposite end flanges to engage in face-toface contact with the opposite ends of said body and of said block and having channel sections therein forming continuations of the opposite ends of said second waveguide portion; and

. assembling said body, said block and said opposite end flanges in said face-to-face contacts to provide the waveguide coupler.

13. The method as defined in claim 12 wherein said mandrel is D-shaped and said apertures are etched through said first layer along the flat side of said mandrel.

14. The method as defined in claim 13 including the step of machining a channel in said block to complement the channel in said body.

15. The method as defined in claim 13 wherein said block is formed as a mirror image of said body by performing steps (a)-(f) on a second, D-shaped mandrel. 

1. A method of making a waveguide coupler including the steps of coating the outer surface of a mandrel having the cross-sectional dimensions and shape of a required first length of waveguide with a thin walled conductive waveguide member; etching a plurality of apertures through a portion of said conductive member; closing said apertures with a soluble material; providing a further conductive material coating to form a second length of waveguide over said apertures; and removing said mandrel and dissolving said soluble material.
 2. A method of making a waveguide coupler including the steps of coating the outer surface of a mandrel having the cross-sectional dimensions and shape of a required first length of waveguide with a thin walled conductive waveguide member; etching a plurality of coupling apertures through a portion of said conductive member; closing said apertures with a soluble material; further coating with another conductive member, removing part of said other conductive member to expose said apertures in said first member and to form a cavity which constitutes part of the interior of said second required length of waveguide; removing said mandrel and dissolving said soluble material; forming a section constituting the remaining part cross-section of said second length and fixing this to said other conductive member to form said second required length of waveguide.
 3. A method of making a waveguide coupler according to claim 2 wherein said cavity constituting part of the interior wall of said second length of waveguide has a depth substantially one half the inside broad wall dimension of said second length of waveguide and said cavity is formed to be of width substantially equal to the narrow wall dimension of said second length of waveguide.
 4. A method of making a waveguide coupler including the steps of coating the outer surface of a mandrel having the cross-sectional dimensions and shape of a required first length of waveguide with a thin walled conductive waveguide member; etching a plurality of apertures through a portion of said conductive member; closing said apertures with a soluble material; providing a further mandrel having the cross-sectional dimensions and shape corresponding with the internal cross-sectional dimensions and shape of a required second length of waveguide to cover said apertures; coating the outer surface of the thin walled conductive waveguide member and the further mandrel with another conductive waveguide member; removing said mandrel and said further mandrel; and dissolving said soluble material.
 5. A method of making a waveguide coupler as claimed in claim 2 wherein the thin walled conductive waveguide member and the other conductive waveguide member are the same material.
 6. A method of making a waveguide coupler as claimed in claim 4 wherein the mandrel and the further mandrel are manufactured from brass and prepared for use by oxidising sufficiently to prevent adhesion of the conductive waveguide members thereto.
 7. A method of making a waveguide coupler as claimed in claim 1 wherein the thin walled inner conductive waveguide member is substantially 0.006 inch thick copper.
 8. A method of making a waveguide coupler as claimed in claim 2 wherein the soluble material is an epoxy resin and the solvent used is methylene chloride.
 9. A method of making a waveguide coupler as claimed in claim 4 wherein the thin walled conductive waveguide member and the other conductive waveguide member are the same material.
 10. A method of making a waveguide coupler as claimed in claim 4 wherein the soluble material is that known under the Registered Trade Mark Araldite and the solvent used is methylene chloride.
 11. The method of making a waveguide coupler, comprising the steps of: a. coating the outer surface of a mandrel with a first, thin layer of conductive material to define interiorly thereof a first waveguide section; b. etching through said first layer to provide a plurality of apertures therein communicating with said first waveguide section; c. blocking off said apertures; d. forming a second waveguide section extending along over said apertures; e. removing said mandrel; and then f. unblocking said apertures to interconnect said first and second waveguide sections through said apertures; the forming of step (d) including coating additional conductive material onto said first, thin layer.
 12. The method of making a waveguide coupler, comprising the steps of: a. coating the outer surface of a mandrel with a first, thin layer of metallic material to define a body of selected length presenting a first waveguide section interiorly thereof; b. etching through said first layer to provide a plurality of apertures therein communicating with said first waveguide section and spaced longitudinally with respect thereto; c. filling said apertures with soluble material; d. coating the outer surface of said body with a second metallic layer which is substantially thicker than said first layer and is integrally joined thereto; e. cutting a channel through said second layer from one end of said body to the opposite end thereof and located to expose said soluble material at the bottom of said channel; f. removing said mandrel from within said body and dissolving away said soluble material; g. forming a block to the length of said body and to engage in face-to-face contact therewith to close the top of said channel and define with the channel a portion of a second waveguide section; h. forming opposite end flanges to engage in face-to-face contact with the opposite ends of said body and of said block and having channel sections therein forming continuations of the opposite ends of said second waveguide portion; and i. assembling said body, said block and said opposite end flanges in said face-to-face contacts to provide the waveguide coupler.
 13. The method as defined in claim 12 wherein said mandrel is D-shaped and said apertures are etched through said first layer along the flat side of said mandrel.
 14. The method as defined in claim 13 including the step of machining a channel in said block to complement the channel in said body.
 15. The method as defined in claim 13 wherein said block is formed as a mirror image of said body by performing steps (a)-(f) on a second, D-shaped mandrel. 